Allelopathy for the sustainable management of agricultural pests: Appraisal of major allelochemicals and mechanisms underlying their actions

Abstract

The global hunger is consistently rising, and also climatic, biotic, and abiotic stress factors are further aggravating this situation by severely impacting crop health and eventually threatening the food security of billions of people. Additionally, the escalating global food demands must be met by doubling food production by 2050. To fulfil this requirement, world agriculture is adopting extensive use of solely chemicals-based fertilizers and crop-protection agents for improving the nourishment of the crops and their protection against deadly weeds and pests respectively. Unfortunately, these unsustainable practices have led to increased biomagnification, bioaccumulation, resistance in most weeds and pests, soil-infertility, and hampered soil-crop-human continuum. Notably, allelopathy, a natural process in which plants release chemicals (primarily recognised for their ability to impact neighbouring plant development), has emerged as a viable long-term technique for controlling key agricultural pests such as weeds, plant-feeding insects, and mites. Despite these facts, the discussion on major allelochemicals and the mechanisms underlying their actions in crops is meager. Taking into account recent literature, this paper aims to: (i) overview allelopathy and the major plant physiological and biochemical responses to important allelochemicals; (ii) enlighten the management of weed via both conventional practices and the modern approaches implying allelopathy; (iii) highlight the major molecular mechanisms underlying the actions of important allelochemicals; (iv) discuss the main plant allelochemicals/ botanicals known to control the major non-weed pests, such as insect pests, nematodes, bacteria and fungi; and (v) also to present the main conclusions of the paper, potential limitations, challenges, and the future prospects. In summary, a critical appraisal of the literature available on the subject confirmed that the allelopathic phenomenon will undergo further exploration as an alternative method for control of major agricultural pests, potentially becoming a part of an integrated, eco-friendly, and organic pest management approach.